one difference between your assumptions and what my thoughts are based on seems to be that that separate vehicle that you cinsider to be too complex seems to be a rocket.

This I do not have in mind. I am simply thinking of usaul production equipment like available in earthian production planst. Such equipment could be adjusted to and improved for Mars. The first time it wouldn't need to be as large as on Earth. It could be carried to Mars component by component and located where the ressources are.

This production equipment would NOT be a vehicle.

All landings as well as all launches would be done from the location where
the procution plant is - and from there all expediations to other locations on Mars would start.

Another difference seems to be that you mainly think of the deposites of water ice at the poles - but there are deposites closer to the equator also - Mars Express for example detected a possible ice sea closer to the equator in 2004 or even later.

Then there is a third point. Ass ar as I am informed the martian dust consists of chemicals where hydrogen and oxygen is bound in - so the dust might be a source of LOX/LH2 - and the dust is ubiquuitous on Mars. May be that also ingredients for other propellants are bound in those chemicals so tat the water could be saved to get potable water and water for production plants and so on.

Finally methane has been found in the martian atmosphere. It will be possible to detected the places where it is released into the "air" - then it can be mined directly. May be that microbes produce it which would enable to cultivate them and get methane without carry the production equipoment from Earth. Then the compexity would be even less than that which is solved on Earth.

The other problem with this, as Campbelp2002 notes, is that most of the water ice is at the martian poles. A system which shuttles back and forth between Mars and Earth should be as energy efficient as possible. It takes a lot more energy to land at the poles of a planet than it does to land near the equator, because you have to burn lots of fuel making plane changes.

I thought substantial ice deposites had been found nearer the Martian equater? I seem to remember reading about a frozen lake under a cap of dust.

Also isn't there a lot of frozen CO2 at the poles which would have to be separated from the water ice?

My thinking was to harvest ice from an area around a stationary refinary, I see little to be gained from travelling more than a couple of hundred metres in any direction. Of course this supposes that the deposites are close together or that a single deposite is large enough to support a refinary for some time.

I think that if deposites are some distance apart then you would need to be able to move the whole plant or it wont be worth doing. Building a processing plant that only has a very limited output would be a waste of effort.

_________________A journey of a thousand miles begins with a single step.

Of courser the Lander tanker has to make more than 7 trips for each Orbital tanker, but the trips are a lot shorter so this should work out fine.

This is quite possible to do technically.

Actually, I would probably put the Mars depot a bit higher to even out the dV load between the 2 vehicles, and carry more payload fuel on the Lander to reduce the number of trips. The Lander should always have a lower MR though, because it needs landing legs, and a higher thrust to weight ratio.

Even better still would be putting the Earth depot at L2, L4 or L5. You could eliminate any need for aero-braking the Orbital vehicle at either end.

I am partly back now after moving houses. In case you really have water in large quantities on Mars (I remain sceptical until real proofs come up, currently only indications are shown), you would still need some kind of bulk mining to get that water.
Harrison Schmitt describes several procedures of bulk mining in his book "Return to the moon" but all have one thing in common.
You would need a service and operators team there. One can imagine that easily. Just look at the next construction site: How often parts have to be repaired or replaced when they are worn out.
So you need a significant human outpost there and that means that you already have a relatively cheap transportation system.
Technology is not the problem, we have that level that is needed, we "only" would have to develop and build the hardware and procedures to get there, but the main hurdle is like Burt Rutan states: "The will to do it". And that will is easier to get when things are cheaper.
So I think my assumption to bring hydrogen for that fuel factory from Earth to Mars is quite valid. Otherwise you would already have a relatively cheap and especially large transportation system from Earth to LEO.

_________________"The hardest hurdle to space isn't the technicalities and money. But rather, the courage and the will to do it." - Burt Rutan.

one question is how much the equipment required to mine weighs. Ass ar as I know there are several different methods to get hydrogen on Earth. One of them is electrolysis of water.

I have problems to imagin electrodes weighing tons or lots of kilograms. The next point is the tank to store the hydrogen in - this simply can be the tank the vehicle has nonetheless.

The other sources of hydrogen except water I already mentioned are the martian soil as well as minerals identified by Spirit and Opportunity. It might be possible to handle them the same way one team competing for the Centennial Challenges Prize for getting lunar oxygen: Heating them up to 2,500Â° C where each molecule cracks into the chemical elements it consists of. This would mean to get the hydrgen easyly.

This means that possibly no lots of water are required.

There were articles under www.space.com talking about looking for the sources of methane that has been detected in the martian atmosphere. If this is done no equipment to get martian hydrogen out of water etc. would be required because a vehicle could land close to the places where methane is released and gather that methane.

Aren't there future opportunities to test light-weight equipments for electrolyses, gathering and fuelling the products? What about enhancing the planned sample return mission to such an experiment that could be left on Mars? Whgat about at least one extra mission to do such a test?

As you have no giant lakes at the surface you'll need a bit more than just a water pump exaggerated expressed. So you'll have to grab the soil in a form of strip mining. That's technically easy but it requires bulky, robust machines that also get serviced as parts will need repairs or replacements.

_________________"The hardest hurdle to space isn't the technicalities and money. But rather, the courage and the will to do it." - Burt Rutan.

what about the chemicals in the soil the molecules of include hydrogen? Alternatively what about the methane released at loactaions yet to be looked for? Using these might remove the need to mine water

What do you think about those non-water-ressources of hydrogen or methane?

Regarding the evidence or indication of water - are the measurements that laed to the result that there are ice layers at the source pole that are a few kilometers thick indication or evidence? I suppose that other regions of Mars are investigated the same way in the past or the future which in particular includes the ice sea that up to now is identified by the structure to be seen on images - that place can be investigated the same way. May be that not Mars Express can do that but there are or will be other instruments that can do that. One american probe carries them - may be MRO.

If you extract something out of the soil, you still have to mine that soil in large quantities which leads to the basically same infrastructure. Technically easy but nonetheless it requires a human outpost.
Just think back at the last shuttle mission as the solar panel was folded. Without human intervention, the panel would have been presumably a loss. Our robotics technology on the other side is far away from doing such unplannable tasks.
I think it's then much simpler to just transfer the required hydrogen from Earth to Mars. The propellant factory itself doesn't need to handle these mechanical high loads, so that can run automatically. I don't know if that was already mentioned. For a past US Mars probe an ISRU experiment was planned but dropped before launch.

About the evidence of water: I would say that these are all indications because they conclude from some "optical" appearing to the result: water. They didn't proof the water itself (like drilling a hole and analyzing that). The next step should be such a probe, perhaps the repeat of the Deep Impact (were they called so? I'm not sure) probes that got lost.

_________________"The hardest hurdle to space isn't the technicalities and money. But rather, the courage and the will to do it." - Burt Rutan.

from my point of view there are significant difference between the folding of the solar array of the ISS and the extraction of soil or something out of that soil. The first of those two was something required during the construction of the ISS - it does not occur very often and not routinely but during construction only and later for maintenance perhaps when arrays have to be replaced by new ones which I suppose to occur after longer periods of time only. And it is done during construction while the extraction of soil will be done AFTER construction of the robot doing the extraction.

Since the extraction will be something that will be done very often and very routinely like the rolling of rovers over Mars it will tested out and put to stress tests very much, very often, very intensively and under very harsh environmental conditions to make sure that it works on Mars without direct human control.

The first time something like that will be tested on another planet might or will be on the Moon. Ass r as the extraction robot will have to move the experiences and insights by Spirit and Opportunity will be involved to reduce the risks of damage and being trapped in a sand dune. There will be at least one additional rover before the robot that will or would extract martian soil to produce LH2, methane etc.

Plus there is the idea of that italian (?) scientist how hydrocarbons could be made out of CO2 and other components of air.

I just wanted to show that things will get much simpler with human interaction and that some things require human interaction unless you accept to replace the complete infrastructure every few weeks.

Mining operations will wear things down, that is unavoidable. Just look at the bulk mining operations on Earth. The bucket of a excavator e.g. has to be replaced at certain intervals.

Edit: I checked the ISRU experiment. It was developed for Mars Surveyor 1 but was delayed before the flight to Mars Surveyor 2, which was cancelled after the failure of Mars Surveyor 1. It exists in a fully developed and built flight configuration so it's quite possible that it will be included in one of the next missions to Mars.

_________________"The hardest hurdle to space isn't the technicalities and money. But rather, the courage and the will to do it." - Burt Rutan.

if the mining operations wear the equipment down or not depends of the environment as well as the technology applied from my point of view.

On Mars gravity as well as impact by weather and climate are much smaller than on Earth - the pressure is much lower, the atmosphere is by far not that oxidizing or corrosive and the climate is more constant than here.

Spirit and Opportunity show that technologies can survive there very long without loosing significant portions of their scientific capabilities. In particular electronics seem to have NOt that a hard time.

The only parts that are worn down significantly is one wheel and one tool-arm - so let's think about those two in short.

1. Wheel(s)

ISRU-equipment to produce propellants don't have to move that much and that far as Spirit and Opportunity had up to now. They also might use tracks instaed of whells or even fly along the ground at an altitude of one or a few meters only and a distance of a few tens or hundreds of meters only.

2. Mining Equipment

The equipment to do the mining might much different to what's applied on Earth. I still have in mind the approacj to heat soil to 2,500Â° C which one team has in mind for the Moon. Assumed it can be achieved on Mars too by simply using more mirrors, adding some lenses and so on the soils could be heated directly - perhaps. This means that it might be avoidable to extract the soil - it simply could b

e heated where it is perhaps. Then the soil would evaporate. To catch this evaporating soil the heating could be done after a transparent dome or container is placed over the small area to be heated.

As soil evaporates a hole is got into which the dome/container could sink to get to more soil. May be that asafe way could be found to move the dome/container horizontal instead of into the deep where microbes might be hurt.

The evaporated soil in the dome/container could be pulled into another part of the equipment separatedly - the elements the chemicals of the soil consist of have different weights enabling that. To do so would mean to store each elemetn apart from all the others. Then hydrogen and other gases can be liquified.

There may be more ways to avoid digging, drilling etc.

Regarding the methane found in the atmosphere no diging etc. is required at all - when the places where methane is released are known the mining equipment simply can place the dome/container there and force the metahne into the store directly as it leaves the martian ground.

Up to here this all means that the stresses for the equioment might be kept below the stresses for the tool-arm at least.

If it turns out one day that the methane is produced by microbes those microbes could be cultivated to make them produce metahne within the containers or domes directly - then the methane could be gathered in much higher concentrations and thus more efficiently. If on the other hand it turns out that the source of the methane is abiotic it might be possible and sufficient to artificially remove ways the methane can be released by and to improve other ways it can be released by.

You could use some of the stored hydrogen that has been processed to fill balloons and then float to the next location, once there you could use the same compressor to re-liquify the hydrogen back into its storage tank that was used during the original extraction.

With the addition of a small thruster or electric motor to drive a propeller you could cover a wide area. This would have the added bonus of gaining information about martian wind speeds and directions as well as getting close up images over a wide terrain.

You could even drop such a platform into the recently discovered caves and mountain ranges or craters would be no problem to navigate.

Perhaps JPowell could comment on the feasibility of the above and how bg a ballooon would be needed to lift a platform weighing a 1000kg for instance. I guess the balloon material itself would need to be included in weight calculations and I'm guessing that this would need to be made of a tougher material than normal due to the Martian temperatures/dust.

_________________A journey of a thousand miles begins with a single step.

for lunar liftoff uses, aluminium-based solid/slurry/gel rockets have sometimes been discussed.
the required ingredients ( O2 and Al ) are in wide abundance on moon.
however, they are reportedly technically very difficult to pull off.
http://yarchive.net/space/rocket/fuels/ ... _fuel.html

I just this moment read two of the links you list and now think that it might be not that difficult today.

There are teams working on the Centennial Challenge Prize to excavate lunar dust and on the extraction of oxygen off this dust. One concept is to heat the dust by mirrors to more than 2,500Â° C. This should allow also to extract aluminum.

Then all the elements can be separated from each other like on Earth. Next the aluminum needs to be turned into powder and then into solid propellant similar like that of the SRBs. Then comapnies like Micro Space could fuel rockets with it if they have subsidiaries on the Moon.

The job of excavation and extraction might be done by companies like Shackleton Crater Company.